Provided is a last round bolt hold-open mechanism for a firearm with a removable ammunition magazine and a longitudinally reciprocating bolt that automatically releases the bolt when a loaded ammunition magazine is inserted. The mechanism includes a frame mountable to a firearm receiver and having a pair of mounting flanges. A catch member is pivotally mounted on a pivot axle oriented transverse to the longitudinal reciprocation of the bolt and carried by the mounting flanges. The catch member has a rearward portion that moves between bolt blocking and bolt release positions and is spring biased toward the bolt blocking position. A forwardly extending finger is configured to be lifted by the presence of at least one ammunition cartridge in the magazine and, when lifted, causes the catch member to pivot to the bolt release position.

An adapter for an M240 machine gun to position the trigger housing assembly distally forward as well as an extended trigger housing assembly for an M240 machine gun and an M240 machine gun with the trigger housing assembly positioned distally forward from the proximal end of the receiver.

A rotating bolt firearm may be configured to fire a .308 cartridge. However, the firearm may have a reduced weight in comparison to standard .308 rifles. The firearm may have many components typically used in a .223 rifle. The firearm may include a barrel extension with an extractor gap, which allows a .308 bolt to fit within a .223 sized barrel extension. The firearm may comprise an elongated magazine well in comparison to a .223 mil-spec rifle. The firearm may weigh less than 6.8 pounds with a 16 inch barrel, or less than 6.3 pounds with a 10.5 inch barrel.

A rotating bolt firearm may be configured to fire a .308 cartridge. However, the firearm may have a reduced weight in comparison to standard .308 rifles. The firearm may have many components typically used in a .223 rifle. The firearm may include a barrel extension with an extractor gap, which allows a .308 bolt to fit within a .223 sized barrel extension. The firearm may comprise an elongated magazine well in comparison to a .223 mil-spec rifle. The firearm may weigh less than 6.8 pounds with a 16 inch barrel, or less than 6.3 pounds with a 10.5 inch barrel.

A bullpup shotgun which ejects shells from the bottom of its action has a reciprocable cover which, when in a closed position, overlies the breech end of the shotgun's barrel. When in an open position, the cover is in spaced relation to the barrel breech end, allowing access to the shotgun's action to clear an ammunition feed malfunction. The cover is mounted on a butt stock, and the butt stock may be movable relatively to the shotgun's receiver to effect motion of the cover between the open and closed positions.

A bullpup shotgun which ejects shells from the bottom of its action has a reciprocable cover which, when in a closed position, overlies the breech end of the shotgun's barrel. When in an open position, the cover is in spaced relation to the barrel breech end, allowing access to the shotgun's action to clear an ammunition feed malfunction. The cover is mounted on a butt stock, and the butt stock may be movable relatively to the shotgun's receiver to effect motion of the cover between the open and closed positions.

A biased pivoting spent ammunition cartridge case extractor and retainer mechanism for blowback bolt firearms. The mechanism includes a distal arcuate hook shaped and dimensioned to intimately engage and nest into part of the circumferential groove in front of the cartridge rim. The hook remains engaged during blowback extraction of the casing from the chamber, and prior to ejection of the case from the firearm. The hook is formed onto the distal end of a rocking member secured to the bolt by a medial pivot. A compression spring bears against the opposite, proximal end of the rocking member thereby biasing the hook inwardly toward the counterbore seat on the distal end of the bolt into which the base of the case rests during extraction. A direct gas impingement system overcomes the biasing force of the spring to cause the case to be ejected.

An improved bolt and bolt carrier with integral gas key having an extension nozzle threadedly secured and pinned to the gas key for use with a direct gas operated firearm is provided. The extension nozzle is designed to receive a portion of the host firearm's gas operating system. The firing pin retaining pin is oriented so as to expose its widest profile to the firing pin's annular flange, increasing its service life. The bolt has a plurality of lugs extending from its forward end. The extractor recess is constructed so that the face of the bolt is round and the adjacent lugs fully supported. The extractor engages approximately 17% more of a seated ammunition cartridge's rim as compared to the prior art AR15/M16 extractor. The result is an improved bolt and bolt carrier which provides for increased operational reliability.

An improved bolt and bolt carrier with integral gas key having an extension nozzle threadedly secured and pinned to the gas key for use with a direct gas operated firearm is provided. The extension nozzle is designed to receive a portion of the host firearm's gas operating system. The firing pin retaining pin is oriented so as to expose its widest profile to the firing pin's annular flange, increasing its service life. The bolt has a plurality of lugs extending from its forward end. The extractor recess is constructed so that the face of the bolt is round and the adjacent lugs fully supported. The extractor engages approximately 17% more of a seated ammunition cartridge's rim as compared to the prior art AR15/M16 extractor. The result is an improved bolt and bolt carrier which provides for increased operational reliability.

The rifle system comprises a rifle and an ammunition round for operation with the rifle. The high pressure ammunition round further comprises a cartridge case having an outer wall wherein prior to firing of the ammunition round, the outer wall geometry of the cartridge case is devoid of features configured for interfacing with a mechanical extractor. The rifle further comprising a barrel chamber which fully supports a chambered cartridge case and a rear extraction mechanism for extracting a spent cartridge case through the rear of the barrel chamber.